Impeller and method for manufacturing impeller

Abstract

The impeller, in particular an impeller (1) for a centrifugal pump, comprises a front plate (2) and a back plate (3) arranged coaxially with a central axis of the impeller and rigidly connected to each other by a plurality of radial blades (4) angularly distributed about the central axis. The front plate has a central through opening (7) adapted to connect the impeller to a drive shaft. The impeller includes a reinforcement (10) extending around the central through opening and at least partially covering the front plate. The front plate and the reinforcement are constructed from a single piece formed by stamping, folding and flattening a metal sheet.

Description

[Technical field]

[0001] The present invention relates to an impeller and a method for manufacturing an impeller, in particular for a centrifugal pump. [Background technology]

[0002] As is known, a centrifugal pump is a hydrodynamic machine in which mechanical energy is exerted on a fluid at the input to the pump by centrifugal acceleration imparted to the fluid by the rotation of one or more impellers. In fact, the job of each impeller is to draw fluid from an inlet duct and to transmit to the fluid the mechanical energy transmitted by the motor in the form of kinetic energy. A centrifugal pump may have a single impeller in a single stage configuration, or multiple impellers arranged in series, in which case the centrifugal pump is referred to as a multi-stage pump.

[0003] An impeller is essentially a rotating element with blades having a generally radial extension and forming branching ducts. Impellers may be manufactured in several structural variations depending on the requirements and the performance required. In particular, impellers made from stamped sheet metal are generally made of a pair of disk-shaped plates axially opposed to one another to form a gap, with radial blades rigidly connecting the two plates. Additionally, a hub or equivalent coupling device is provided at the center of each impeller for enabling the impeller to be secured to a drive shaft operatively connected to a motor means.

[0004] With regard to torque transmission, prior art impellers made from stamped sheet metal are essentially of two types. According to the first type, the basic disk of the impeller, i.e. the plate designed to transmit torque between the blades and the drive shaft, is made with a thickness sufficient to withstand the stresses. According to the second type of construction, reinforcing elements are welded in the areas allocated for stress transfer, so that the required thickness of the material is reached only in localized areas. When the stresses are such that it is uneconomical to solve the torque transmission problem simply by increased thickness, the second type of construction is generally adopted.

[0005] While the above technologies solve some of the problems cited above, they involve high manufacturing costs and manufacturing processes that sometimes also involve external suppliers, with obvious problems and risks associated with supply. Additionally, the above techniques generally involve an increase in the overall weight of the impeller.

[0006] US Patent No. 5,399,633 discloses a method of manufacturing a centrifugal pump that includes cutting both the blade and cover body from a metal sheet and assembling them in place. The blade is then welded to the cover body using a laser beam that is directed at the side of the cover body opposite the point of contact with the blade. A second cover body is welded to the blade in a similar motion as the blade is welded to the first cover body.

[0007] Patent Document 2 discloses an impeller assembly having two disk members with different diameters, arranged coaxially with the axis of rotation and facing each other to form a gap. The blades are arranged radially within the gap. The two disk members are also provided with fastening means in their centers for fastening to a transmission shaft rotating about the axis of rotation. The contoured vanes have a minimum diameter and protrude radially from the peripheral area of ​​the disk members arranged on the blades.

[0008] Patent document 3 discloses a method of manufacturing a light-weight annular flange plate into which a boss portion is fitted by pressing an annular thin plate on which a cylindrical protrusion is formed by processing a material and buckling the cylindrical protrusion.

[0009] No. 5,399,633 discloses a metal member defining a hole, in which the hole is reinforced by forming a flange and folding the flange back so that a rolled outer surface of the flange defines a perimeter of the hole. The sheared edge is spaced from the perimeter of the hole. The shaft of a fastener inserted into the hole contacts the unsheared surface. A reinforcing ring can be assembled around the flange. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] German Patent Publication No. 4446193(A1) [Patent Document 2] U.S. Patent Application Publication No. 2017 / 260992(A1) [Patent Document 3] Japanese Patent Publication No. 58-84618 [Patent Document 4] U.S. Patent Application Publication No. 2012 / 315109(A1) Summary of the Invention

[0011] The object of the present invention is to provide an impeller, in particular for centrifugal pumps, and a method for manufacturing an impeller, which overcomes the drawbacks of the cited prior art. Within this objective, a particular goal of the invention is to provide an impeller and a method which makes it possible to obtain a good compromise between the need to reduce the manufacturing costs and weight of the impeller and the need to ensure the necessary mechanical properties for the impeller. A further goal of the present invention is to provide an impeller and method that allows for minimizing process time and maximizing the total production capacity of the system. It is a further goal of the present invention to provide an impeller and method that is safe, efficient, and relatively simple to operate.

[0012] This object and these aims, as well as others that will become more apparent hereinafter, are achieved by an impeller, in particular for a centrifugal pump, comprising a front plate and a back plate arranged coaxially with a central axis of said impeller and rigidly connected to one another by a plurality of radial blades angularly distributed around said central axis, said front plate having a central through opening adapted to connect said impeller to a drive shaft, said impeller comprising a reinforcing part extending around said through opening and at least partially covering said front plate, said front plate and said reinforcing part being constituted by a single piece of stamped, bent and flattened metal sheet.

[0013] The object and goal of the present invention is also a method for manufacturing an impeller, in particular for a centrifugal pump, said impeller comprising a front plate and a back plate arranged coaxially with each other and rigidly connected to each other by means of a plurality of radial blades angularly distributed around the central axis of said impeller, said front plate having a central through opening predetermined for the connection of said impeller to a drive shaft, The method comprises: a) forming said front plate and associated through apertures by stamping a sheet of metal; b) forming said backplate by stamping a sheet of metal; c) forming said radial blades by stamping a sheet of metal; d) rigidly connecting said radial blades to one of said front plate and said back plate such that said radial blades are angularly distributed about said central axis of said impeller; e) rigidly connecting said radial blades to one another between said front plate and said back plate; Including, The method further comprises the step a) of: a1) folding at least a portion of excess material from at least a portion of an edge area of ​​said through opening; a2) flattening the portion of excess material folded during step a1) on said front plate, thereby forming a reinforcement extending around said through opening and at least partially overriding said front plate; This is achieved by a method comprising the steps of:

[0014] Further features and advantages will become more apparent from the description of preferred, but not exclusive, embodiments of the impeller according to the invention, illustrated by way of non-limiting example in the accompanying drawings, in which: [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a perspective view of components of an impeller according to the present invention; [Diagram 2] FIG. 2 is another perspective view of the components of FIG. 1. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of a detail of a component of FIGS. 1 and 2; [Figure 4] FIG. 2 is an exploded view of an impeller according to the present invention. [Diagram 5] FIG. 5 is a perspective view of the impeller of FIG. 4. [Figure 6] FIG. 6 is another perspective view of the impeller of FIGS. 4 and 5. [Figure 7] FIG. 2 is a front view of an impeller according to the present invention. [Figure 8] FIG. 8 is a diametrical cross-sectional view of the impeller of FIG. [Figure 9] FIG. 2 is a perspective view of multiple impellers mounted on a drive shaft of a multi-stage pump. [Figure 10] FIG. 13 is a front view of another embodiment of an impeller according to the present invention. [Figure 11] FIG. 11 is a diametrical cross-sectional view of the impeller of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] With reference to the figures cited, the reference numbers 1 and 101 generally indicate an impeller, in particular adapted for use in a centrifugal pump. For example, the impeller 1, 101 may be mounted in a multi-stage centrifugal pump, known per se and not shown, where each stage includes an impeller of the type according to the invention, pre-set to rotate in a respective chamber, as shown by way of example in FIG. However, it will be apparent to those skilled in the art that the impeller 1, 101 or an equivalent structure may be used to advantage in other types of hydrodynamic machines.

[0017] The impeller 1, 101, advantageously made from stainless steel sheet, comprises a front plate 2, 102 and a back plate 3 arranged coaxially along its central axis 50.

[0018] The front plate 2, 102 and the back plate 3 are rigidly connected to one another by a number of radial blades 4, for example by spot welds 5.

[0019] It will be clear to one skilled in the art that in alternative embodiments not shown, the radial blades 4 may also be provided integrally with either the front plate 2, 102 or the back plate 3.

[0020] The radial blades 4 are angularly distributed about a central axis 50 and preferably extend along a helical or generally curvilinear path.

[0021] The front plate 2, 102 is substantially disc shaped and advantageously has a peripheral profile shaped to reduce the axial thrust forces generated during pumping.

[0022] For example, in the embodiment shown in Figures 1 to 9, the front plate 2 has a substantially sawtooth profile formed by alternating first curved portions 6a that are substantially parallel to the radial blades 4 and second curved portions 6b that are transverse (transverse) to the blades 4.

[0023] In the example shown in Figures 10 and 11, an impeller according to the invention is designated by reference number 101, components having the same structure and function as those in Figures 1 to 9 are designated by the same reference numbers, and the front plate 102 has substantially a lobate profile formed by alternating recesses 106a provided between the radial blades 4 and circular portions 106b.

[0024] In alternative embodiments not shown, it will be apparent to those skilled in the art that an impeller according to the present invention may include a front plate having a different profile than that illustrated herein.

[0025] The front plate 2, 102 has a front through opening 7 designed to connect the impeller 1, 101 to a drive shaft 60 which, in use, is operatively connected to a motor means (not shown) for rotating the drive shaft. Advantageously, the contour of the through opening 7 is substantially complementary to the cross-sectional contour of the drive shaft 60 .

[0026] The back plate 3 has a through opening 7 and a central through hole 8 having a diameter larger than that of the drive shaft 60 . The through hole 8 together with a collar 9 extending from the through hole 8 form an inlet channel for the impeller 1 .

[0027] According to the invention, the impeller 1,101 comprises a reinforcement 10 which extends around the through opening 7 and at least partially covers the front plate 2,102.

[0028] Also according to the invention, the front plate 2, 102 and the reinforcement 10 are constituted by a single piece formed by stamping, folding (or folding over) and flattening a metal sheet, as will become more apparent below. That is, the reinforcing portion 10 is substantially annular, and has a through opening 7 at the center. The reinforcing portion 10 is in complete contact with the front plate 2, 102.

[0029] Advantageously, the effect of folding and subsequent flattening is a work-hardening of the material at the folding line between the reinforcement 10 and the front plate 2, 102, which results in an increase in its mechanical strength. Experimental tests carried out by the applicant have shown that the effect of work hardening is to increase the hardness of the material by a factor of two or three over that of the starting material.

[0030] A further important advantage of the impeller 1, 101 is that the surface of the inner surface of the through opening 7 designed to come into contact with the drive shaft 60 is doubled (or redoubled) since it is defined by the overlapping of the reinforcement 10 on the front plate 2, 102. In this way, the torque-induced contact pressure between the drive shaft 60 and the impeller 1, 101 is significantly reduced.

[0031] Based on the above, the method for manufacturing an impeller according to the invention comprises step a) of forming a single part by stamping a metal sheet, the single part forming the front plate 2, 102 and its corresponding through opening 7.

[0032] As previously mentioned, the front plate 2, 102 has a substantially disk-like shape with a peripheral profile shaped to reduce the axial thrust generated during pumping.

[0033] The through opening 7 has edges that are substantially complementary to the cross-sectional profile of the drive shaft 60 .

[0034] According to the invention, the method comprises a step a1) of folding or folding at least a portion of the excess material away from at least a portion of the edge area of ​​the through opening 7 . Preferably, the excess material from the entire edge of the through opening 7 is folded over.

[0035] The method further comprises a step a2) in which the previously folded excess material is flattened onto the front plate 2, 102 so as to form a reinforcement 10 extending around the through opening 7 and at least partially cover the front plate 2, 102.

[0036] In practice, the excess material is deformed until it forms a reinforcement 10 , which appears substantially like an annular element that fits completely to the front plate 2 , 102 . It looks like. Due to the strong compression of the material, no radius is formed at the edges, as shown for example in FIG.

[0037] The method according to the invention also comprises the further step b) of forming a single piece by stamping a metal sheet, such single piece forming the backplate 3 and the collar 9 forming the through hole 8 .

[0038] The method according to the invention also comprises the further step c) of forming the radial blades 4 by stamping the metal sheet.

[0039] The method according to the invention also comprises two additional steps d) and e) of rigidly connecting the radial blades 4 to the front plate 2, 102 and the back plate 3.

[0040] Steps a), b) and c), as well as steps d) and e), do not have to be performed in exact order relative to one another, it makes no difference to perform one or the other first, or all at the same time.

[0041] Steps a), a1) and a2) must be performed consecutively.

[0042] The stamping is preferably cold stamping, although hot stamping may be used as well, with subsequent treatments to harden and temper the material.

[0043] The method according to the invention makes it possible to obtain localized reinforcement in the areas of the front plate 2, 102 where increased stiffness and mechanical strength are required, while minimizing the cost and overall weight of the impeller 1, 101.

[0044] In fact, it has been found that the present invention provides an impeller and a method for providing an impeller, in particular for centrifugal pumps, which achieves the intended objects and aims and makes it possible to achieve a good compromise between the need to reduce the manufacturing costs and weight of the impeller and the need to ensure the necessary mechanical properties of the impeller.

[0045] In particular, the invention allows a smaller thickness of the raw material for equal mechanical properties compared to the prior art.

[0046] Also, from an industrial management point of view, the present invention makes it possible to use only one code, avoiding the need to manage three different codes for each basic disc (front plate, hub and assembly).

[0047] A further advantage is that the present invention does not require the process of welding the hub, and the front plate and reinforcement can be integrally formed by using virtually any press, as long as suitable pressure and a suitable resting surface are provided.

[0048] This application claims priority to Italian Patent Application No. 102021000015179, filed June 10, 2022, the subject matter of which is incorporated herein by reference. [Explanation of symbols]

[0049] 1,101 impellers 2,102 Front Plate 3 Backplate 4 Radial blades 7 Through hole 8 Through holes 10 Reinforcement 60 Drive shaft

Claims

1. An impeller, in particular an impeller for a centrifugal pump, comprising a front plate and a back plate arranged coaxially with a central axis of the impeller and rigidly connected to each other by a plurality of radial blades angularly distributed around said central axis, said front plate having a central through opening adapted to connect the impeller to a drive shaft, the impeller includes a reinforcement portion extending around the through opening and at least partially covering the front plate; 11. An impeller, comprising: said front plate and said stiffener comprising a single piece of stamped, bent and flattened sheet metal.

2. The impeller of claim 1 , wherein the reinforcement portion is substantially annular.

3. The impeller according to claim 1 , wherein the reinforcing portion is completely in contact with the front plate.

4. The impeller of claim 1 , wherein the impeller comprises a portion of work-hardened material extending substantially at a bend line between the front plate and the reinforcement.

5. 5. The impeller of claim 4, wherein the bend line between the front plate and the reinforcement defines a sharp edge.

6. 10. The impeller of claim 1, wherein the front plate has a peripheral profile shaped to reduce axial thrust.

7. 7. An impeller as claimed in any one of claims 1 to 6, characterized in that the backplate has a central through hole having a diameter larger than the through opening and the drive shaft.

8. A method for manufacturing an impeller, in particular an impeller for a centrifugal pump, comprising a front plate and a back plate arranged coaxially with each other and rigidly connected to each other by a plurality of radial blades angularly distributed around a central axis of the impeller, the front plate having a predetermined central through opening for connection of the impeller to a drive shaft, a) forming said front plate and associated through apertures by stamping a sheet of metal; b) forming the backplate by stamping a sheet of metal; c) forming said radial blades by stamping a sheet of metal; d) rigidly connecting said radial blades to one of said front plate and said back plate such that said radial blades are angularly distributed about a central axis of said impeller; e) rigidly connecting the radial blades to one another between the front plate and the back plate; In a method comprising: The step a) a1) folding at least a portion of excess material from at least a portion of an edge area of ​​the through opening; a2) flattening a portion of the excess material folded in step a1) onto the front plate, thereby forming a reinforcement extending around the through opening and at least partially covering the front plate; The method of claim 1, comprising:

9. The method of claim 8, wherein the reinforcement is substantially annular.

10. 10. Method according to claim 8 or 9, characterized in that the reinforcement rests completely on the front plate.

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